1. Technical Field
The present invention relates generally to computer system displays, and more specifically to a technique for displaying windows on a computer display having a minimal amount of support for displaying windows.
2. Background Art
The display of information generated by an application program running on a computer system is often important to the perceived usefulness of the application. Poor displays can render an otherwise good application nearly useless, and good displays can help a user make more efficient use of an application.
Windows are often used to display several items of information on a screen at the same time. Windows are separate regions, often separated by borders, which are treated somewhat independently. Different windows may receive output from different applications running concurrently, and a single application may generate output to several windows.
In general, windows may be displayed as tiled or overlapped. Tiled windows are displayed side-by-side horizontally or vertically, or both, with no overlap of their displayed regions. Overlapped windows appear to be stacked one on top of another, much as individual sheets of paper piled on a desktop, with the covered portions of lower windows not being displayed. This type of display is sometimes referred to as the desktop metaphor for displays, or messy desk windowing. Work stations coming into increasingly common use typically have powerful window display systems to support messy desk windowing.
Many mainframe based applications, typically descendants of applications written before work stations started becoming common, are often written for character based, non-programmable terminals. Some terminals designed for tying into larger, central computer systems support rudimentary graphics or character graphics capabilities, or provide for designating portions of the display screen as active for scrolling purposes. The combination of many available terminals and their software drivers often provides the ability to do an extremely limited form of windowing. This form of windowing, referred to as split screen windowing, typically has full width tiled windows stacked vertically on the screen. These windows often have no borders, and only scrolling of the entire window is allowed.
It would be desirable to provide a windowing system for non-programmable terminals which supports messy desk windowing. It would also be desirable to provide a high level interface for application programs which hides the details of the window system and provides callable services similar to those available on work stations. It would further be desirable for such a windowing system to be efficient on non-programmable terminals.